The effects of hemorrhage on mitogen-induced lymphocyte proliferation.

Bacterial infection often occurs after trauma and hemorrhage and is believed to be a reflection of a compromised host defense system. In the present study, the effect of temporary loss of blood on lymphocyte proliferative capacity was investigated. Hemorrhage was induced in unanesthetized rats with chronically catheterized carotid arteries. Two hours after withdrawal of 30% of total blood volume, phytohemagglutinin-induced lymphocyte proliferation was almost completely suppressed; proliferation remained depressed for at least 24 hrs. The degree of suppression in lymphocyte proliferation was found to be dependent on the duration of hemorrhage. Mitogen-induced proliferation of lymphocytes was significantly reduced as early as 30 min after hemorrhage and became more depressed at 2.0 hr after hemorrhage. This abnormality in host defense mechanisms may contribute to the increased incidence of sepsis present after trauma and hemorrhage.